Found the issue. Don’t know why but it looks likes a bad idea if you change the default ports from nxhtd to 80 and 443 before you start the server once. So the way I see it, the user is configured at the first start of the webserver. The only way for me to fix was to remove nomachine completly with all files, and install it again. After that i started the webserver once. With this user was created, rights were set. So every thing fine.
Hello Kroy, very thanks for your answer. This command works, but unfortunately the same as the original command. What I came up with is that you can then set up the standard Lubuntu Desktop LXQT in the logged-in state per user. This is now a workaround.
But apparently there has to be another command / option that is used by SDDM. Strange.